A series of experiments are proposed in which the nature of human auditory development is investigated using the auditory evoked response (AER). These experiments are divided into four areas of inquiry: 1) Frequency specificity, 2) binaural interaction, 3) scalp topography, 4) fatique/adaptation. The outcome of the frequency specificity section will be a description of the development of auditory responsivity as a function of stimulus frequency. Continuous high pass noise, low pass noise, tones and forward masking paradigms will be used to determine the frequency specificity of the response. In addition, the assumptions underlying the applicability of masking techniques will be tested. The results of these measurements should also constitute frequency specific clinical norms, as a function of age. The outcome of the binaural interaction section will be a description of the time course of maturation of binaural interaction and its dependence upon stimulus frequence. Binaural interaction will also be described in a group of patients with central and peripheral auditory dysfunction. The scalp topography studies will result in a spatio-temporal map of the AER as a function of age and stimulus dependency. This information will assist in the selection of "optimal" recording sites for clinical applications and the investigation of maturation of the auditory tract. The outcome of the adaptation/fatigue section will be description of the time course of maturation of these processes, and their interaction with stimulus variables. Such information should prove useful for the eventual development of noise-risk criteria for infants. As a group, these experiments will result in the creation of a multidimensional developmental space including the time course of maturation and stimulus dependency of each of its dimensions. Such a space not only provides a more complete description of auditory development, but may ultimately provide a more rational basis for the differential diagnosis of diseases affecting the auditory pathway.